<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <style>
    html {
      width: 100%;
      height: 100%;
      border-radius: 20px;
      border: 1px solid red;
      overflow: hidden;
      box-sizing: border-box;
    }
    body {
      border: 5px solid blue;
      border-radius: 50px;
      width: 100%;
      height: 100%;
      overflow: hidden;
      /* background-color: #bfa; */
      margin: 0px;
    }


    .con {
      width: 100%;
      height: 200px;
      box-sizing: border-box;
      border-radius: 100px;
      border: 5px solid red;
      /* overflow: hidden; */
    }
    .item{
      width: 100%;
      height: 100%;
      background-color: green;
    }
  </style>
  <style></style>
  <body>
    <div class="con">
      <div class="item"></div>
    </div>
  </body>
</html>
